Twisted pairs cables include at least one pair of insulated conductors twisted about one another to form a two conductor pair. A number of two conductor pairs can be twisted about each other to define a twisted pair core. A plastic jacket is typically extruded over a twisted pair core to maintain the configuration of the core, and to function as a protective layer. Such cables are commonly referred to as multi-pair cables.
The telecommunications industry is continuously striving to increase the speed and/or volume of signal transmissions through multi-pair cables. One problem that concerns the telecommunications industry is the increased occurrence of alien crosstalk associated with high-speed signal transmissions. In some applications, alien crosstalk problems are addressed by providing multi-pair cables having a layer of electrical shielding between the core of twisted pairs and the cable jacket. Such shielding however is expensive to manufacture; accordingly, unshielded twisted pair cables are more often used.
Without electrical shielding, and with the increase in signal frequencies associated with high-speed transmissions, alien crosstalk can be problematic. Undesired crosstalk in a cable is primarily a function of cable capacitance. As a cable produces more capacitance, the amount of crosstalk increases. Capacitance of a cable is dependent on two factors: 1) the center-to-center distance between the twisted pairs of adjacent cables, and 2) the overall dielectric constant of the cables.